Manufacture of polyhydric alcohols



Patented Nov. 20, 1945 MANUFACTURE or POLYHYDBIO ALCOHOLS Henry Dreyfus, London, England, assignor to Celanese Corporation of America, a corporation of Delaware No Drawing. Application April 19, 1941, Serial No. 889,418. In Great Britain April 83, Mill This invention relates to the manufacture of organic compounds and, more pa tic a y. slycols and other polyhydric alcohols.

According to the invention a hydroxyl-groupcontaining halogen derivative oi a polyhydric alcohol is subjected to the action of heat in presence of coppe or silver in a finely divided and chemically reactive form, so as to eliminate halopen from said compound to produce a polyhydric alcohol of higher molecular weight.

The term polyhydric alcohol includes within its scope the glycols and a most important emc-"i ioent of the invention is the treatment of glycol halo-hydrins and, in particular, the chlorhydrins and bromhydrins, for instance of the ethylene, trimethylene and propylene glycols. From these starting materials other glycols of higher molecular weight are obtained by the process of the invention. For example, from ethylene glycol chlorhydrin there is obtained 1:4-butylene glycol. The invention includes also the treatment of hydroxyl-group-containins halogen derivatives of glycerol and other polyhydric alcohols and especially the monochlor derivatives thereof, e. g. glycerol alpha-monochlorhydrin.

A chemical method may be used to produce the copper or silver in slutable form and reduction of a cuprammonium solution. acidified with acetic acid, by treatment with sulphur dioxide' yields a copper which has been found eflective. Other acids than acetic acid can be used for acidifying the cuprammonium solution, e. g. formic and prop-ionic acids. The concentration of the solution affects the fineness of sub-diviit is desirable to use reaction temperatures i above 100 C. e. g. temperatures of 125-175 C.

or even higher, e, g. 200 C. with some starting materials and products, e. s. when making lz-i-butylene glycol from ethylene chlorhydrin. the reaction can be carried out by boiling the reaction mixture under reflux, vigorous boiling ensuring maintenance of the copper or silver in suspension. The reaction can be carried out under pressure, e. g. by heating the reactants in an autoclave especially when it is desired to employ a reaction temperature above the normal able to avoid as far as possible the presence of water where such water is liable to cause ydrolysis oi the halogen compound to produce the original glycol. A suitable starting material for use in producing 1:4-butylene glycolcan be obtained by distilling an aqueous solution of ethylene chlorhydrln to obtain a solution of high concentration and thereafter extracting the chlorhydrln with a solventof hydrophobe qualsion of the copper produced and it is preferred and preferably a solution of 540% concentration is used. Silver suitable for use in the proces of the invention may be preparedin a similar manner, in this case the suspension of silver salt obtained by acidifying the ammoniacal silver solution being reduced with sulphur dioxide instead of a solution as'in the case-oi copper.

The copper or silver produced may be used while still moist with water used for washing or after drying by treatment with alcohol and then ether. Copper and silver prepared as described are chemically very active and shouldv be stored out of contact with air in order to avoid oxidation.

ities, for instance benzol, subsequently separat ing the substantially anhydrous chlorhydrin thus obtained from the benzol or other solvent by distillation.

The period during which the reactants are heated together may be varied according to the reactivity of the starting materials and according to the conversion desired, since it is sometimes more economical to separate the products at a given stage thantocontlnue the process for a much longer period in order to obtain a higher conversion. Generally, it is preferred to reflux ethylene chlorhydrin with the, copper or silver for somewhat more than 24 hours and preferably for a period oi 40-50 hours, although an even longer period, c. g. up to or '70 hours. ay be used if desired. A somewhat increased conversion for a given heating period may be obtained by adopting a cascade operation. This may be put into practice by heating the chlorhydrin or other organic compound used as start-. ing material with the copper or silver tor a short period, c. g. l-5 hours, and then decanting the quid onto fresh copper or silver and using the r or silver remaining from the first operation for the treatment of fresh chlorhydrin, this operation being repeated a number of times so that eventually a number of vessels are in use in which fresh copper or silver is used for the product which has undergone reaction for the longest period, while fresh chlorhydrin is subiected to treatment with the copper or silver nearest exhaustion, i. e. largely converted into copper or silver halide. Such an operation may be carried out automatically is desired by a suitable arrangement of overflows, so that the chlorhydrin gradually travels through the successive vessels in a continuous manner, while from time to time a vessel containing exhausted copper or silver is removed and a vessel containing fresh copper or silver is replaced at the other end oi line.

Theoretically one atom of copper or two atoms of silver are requiredto combine with each two atomsoi halogen. but in practice it is iounddesirable to use an excess the metal. at least twice the stoichiometrical amount being used and preferably a quantity equal to ior times or even more, e. g. up to 6 or 7. timesthe stoichiometrical amount. 3 V i It has been found advantageous to have present in the reactants a quantity of a strong base. e. g. a caustic alkali, especially whenxmoisture is present. Causticsoda is very eiiective and even small quantities oi this substance'e. g. 4 or 5% on the weight oi-the' reactants. cause a marked improvement in the conversion, while even larger quantites. e. g. up to or produce even better results. The caustic alkali can be added solid or as a concentrated aqueous solution to the reactants. Organic bases and more particularly primary bases, e. g. mono-methylamine. produce a similar effect and rather smaller quantities of mono-methylamdne produce eflects quite as marked-as much larger quantities of caustic soda. For example, 5% on the weight of the reactants oi mono-methylamine is very efi'ectiveinpractice; v tin'ilhe following examples illustrate the inven- Ermnple 1 Production of finely divided and chemically reactive copper: I

100 parts by weight oi crystalline copper sulphate (CusOaoli-iol are dissolved in 3,000parts by weight of water and concentrated aqueous ammonia (0.880 sp. gr.) added until theprecipitote formed just redissolves. .Gla'cial acetic acid is addeduntil the mixture becomes acid and sulphur dioxide is then passed into the mixture. The blue solution becomesdark green'and afine green precipitate is formed which changes colour, passing from yellowish brown to a dual but! colour. The super-natant liquor is decanted from this bun precipitate which is then washed thoroughly with water whilst avoiding unnecessary exposure to air and partially dried by iiltration with suction.

Emmnlez Preparation of ilnely divided and chemically reactive silver: 7

100 parts by weight of crystalline silver nitrate are dissolved in 2,000 grams of water and concentrated ammonia (0.880sp. gr.) is added until the precipitate iirst iormedi redissolves. Glacial acetic acid is then added until the mixture is acid when a white precipitate or silver acetate is Y ample 1, equal to selected irom one medium soas assess? obtained. Sulphur dioxide is passed through this suspension of silver acetate until the latter is reduced to silver, after which the silver is separated and washed as described in connection with the production of copper in Example 1.

Example 3 Production of tetramethylene glycol from ethylene chlorhydrin:

To ethylene chlorhydrin there is added a quantity of the copper prepared according to Ex- 5 times the stoichiometricel chlorine present. 5% of monomethylamine'on the weight of the reactants is then added. and the mixture is heated to boiling under reflux. After refluxing for 48 hours, the product is fractionated and the fraction boiling above 180 C. containing substantially the whole of the tetramethylene glycol formed, being. 001- lected separately. This fraction is then redistilled to obtain the tetramethylene glycol in pure form.

Having described my invention, what, I desire to secure by Letters Patent is: v

1. Process for the production oi a polyhydric alcohol, which comprises subjecting a hydroxylgroup-containing halogen derivative of a polyhydric alcohol containing fewer carbon atoms to the action of heat in presence of a metal selected from the group consisting of copper and silver said metal being prepared in a finely divided and chemically reactiveiorm, by reduction with sulequivalent of the persed in an aqueous medium so as to-eliminate halogen from said compound to produce a polyhydric alcohol oi higher molecular weight.

2. Process for the productionoi a glycol, which comprises subjecting a halohydrin of a glycol containing fewer carbon atoms to the action oi heat in presence of a metal selected from the group consisting of copper and silver said metal being prepared in a finely divided and chemically reactive iorm, by reduction with sulphur dioxide of a compound of the metal dispersed in an aqueto eliminate halogen irom said compound to produce a glycol or higher molecular weight.

ylene glycol, which comprises subjecting ethylene the action of a metalv glycol chlorhydrln to the group consisting oi copper and silver said metal being prepared in a finely d1- vided and chemically reactive form by reduction compound of the metal medium so as to elimiwith sulphur dioxide of a dispersed in an aqueous nate chlorine from said tetramethylene glycol.

5. Process for the production of a glycol, which comprises subjecting a holahydrin of a glycol containingiewer carbonatoms to the action of heat in presence of a metal selected from the group consisting of copper and silver in a fine y divided and chemically reactive form prepared by acidification of an emmoniacal solution 0! a compound to produce salt of the metal with a lower fatty acid, followed by reduction with sulphur dioxide, so as to eliminate halogen from said compound to produce a glycol 01 higher molecular weight.

6. Process for the production of a polyhydric alcohol, which comprises subjecting a hydroiwlgroup-containing halogen derivative of a polyhydric alcohol containing iewer carbon atoms to the action of heat under reflux in presence of a metal selected from the Broup consisting of copper and silver said metal being prepared in a finely divided and chemically reactive form, by reduction with sulphur dioxide of a compound of the metal dispersed in an aqueous medium so as to eliminate halogen from said compound to ll produce a poiyhydric alcohol or higher molecular weight.

7. Process for the production of a glycol, which comprises subjecting a halohydrin of a glycol containing iewer carbon atoms to the action oi. heat in presence of a metal selected from the group consisting of copper and silver said metal being prepared in a finely divided and chemically reactive form by reduction with sulphur dioxide of a compound of the metal dispersed in an aqueous medium in the presence of astrong base, so as to eliminate halogen from said compound to produce a glycol of higher molecular weight.

HENRY DREYFUB. 

